Semiconductor light emission device, image formation apparatus and image display apparatus

ABSTRACT

A semiconductor light emission device includes a substrate, and semiconductor light emission elements mounted on the substrate and each including an anode connection pad and a cathode connection pad. At least one of the anode connection pad and the cathode connection pad has a fine shaped portion. An image formation apparatus and an image display apparatus are described using the semiconductor light emission device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority based on 35 USC 119 from prior JapanesePatent Application No. 2011-260567 filed on Nov. 29, 2011, entitled“SEMICONDUCTOR LIGHT EMISSION DEVICE, IMAGE FORMATION APPARATUS ANDIMAGE DISPLAY APPARATUS”, the entire contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure relates to a semiconductor light emission device havinga semiconductor light emission element mounted on a substrate, andrelates to an image formation apparatus and an image display apparatususing this semiconductor light emission device.

2. Description of Related Art

There is a print head of an electrophotographic printer that uses an LEDarray having LEDs arranged in a line. In such a print head (LED arrayhead), an LED array and a drive circuit are connected with each other bywire bonding. Integral formation of the LED array and the drive circuitcan reduce the numbers of bonding pads and wires.

As a semiconductor light emission device used for an LED array head,there has recently been proposed a semiconductor light emission devicein which a thin-film semiconductor light emission element is fixed by anintermolecular force to a surface of a mount substrate having a wiringportion formed therein in advance. The thin-film semiconductor lightemission element and the wiring portion are connected with each other byusing thin-film wiring (see Document 1: Japanese Patent ApplicationPublication No. 2005-79262 (see FIG. 2), for example).

In a semiconductor light emission device disclosed in Document 1, athin-film semiconductor light emission element having a light emissionportion and a dedicated electrode (pad) formed therein is fixed by anintermolecular force to a surface of a mount substrate having a wiringportion formed therein. The dedicated electrode of the thin-filmsemiconductor light emission element is connected to the wiring portionof the mount substrate by using thin-film wiring. Additionally, in orderto facilitate the electric connection of the thin-film semiconductorlight emission element when mounted in a misaligned position, thededicated electrode of the thin-film semiconductor light emissionelement has a larger area than the light emission portion.

SUMMARY OF THE INVENTION

However, the dedicated electrode is a metal, and has a larger thermalexpansion coefficient than other parts of the thin-film semiconductorlight emission element. For this reason, when the dedicated electrode isformed to have a large area, a stress acts on the thin-filmsemiconductor light emission element due to thermal contraction in themanufacturing process, and thereby warpage or cracks may occur in thethin-film semiconductor light emission element. In addition, when largewarpage occurs in the thin-film semiconductor light emission element,the thin-film semiconductor light emission element peels off from themount substrate, thereby leading to a reduction in yield.

An object of an embodiment of the invention is to achieve improvement inyield by preventing the occurrence of warpage or cracks in the thin-filmsemiconductor light emission element.

An aspect of the invention is a semiconductor light emission deviceincluding: a substrate; and semiconductor light emission elementsmounted on the substrate and each element including an anode connectionpad and a cathode connection pad. At least one of the anode connectionpad and the cathode connection pad has a fine shaped portion.

This aspect of the invention can achieve improvement in yield bypreventing the occurrence of warpage or cracks in the thin-filmsemiconductor light emission element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a semiconductor light emission device of afirst embodiment of the invention.

FIG. 2 is an enlarged plan view showing the semiconductor light emissiondevice of the first embodiment.

FIG. 3 is a cross-sectional view taken along the line III-III in adirection indicated by arrows shown in FIG. 2.

FIG. 4 is a cross-sectional view taken along the line IV-IV in adirection indicated by arrows shown in FIG. 2.

FIG. 5 is a plan view showing a thin-film semiconductor light emissionelement of the first embodiment.

FIG. 6 is a plan view showing a semiconductor light emission device of acomparative example.

FIG. 7 is a plan view showing a thin-film semiconductor light emissionelement of a second embodiment of the invention.

FIG. 8 is a plan view showing a thin-film semiconductor light emissionelement of a modified example of the second embodiment.

FIG. 9A is a plan view showing a thin-film semiconductor light emissionelement of another modified example of the second embodiment. FIG. 9B isa plan view showing an anode connection pad of anther modified exampleof the second embodiment. FIG. 9C is a plan view showing a cathodeconnection pad of anther modified example of the second embodiment.

FIG. 10 shows a semiconductor light emission device of a thirdembodiment of the invention, and is a cross-sectional view taken alongthe line in a direction indicated by arrows shown in FIG. 2.

FIG. 11 shows the semiconductor light emission device of the thirdembodiment, and is a cross-sectional view taken along the line IV-IV ina direction indicated by arrows shown in FIG. 2.

FIG. 12 is a cross-sectional view showing a print head using thesemiconductor light emission device of the first, second or thirdembodiment.

FIG. 13 is a diagram showing a configuration of an image formationapparatus using the print head in FIG. 12.

DETAILED DESCRIPTION OF EMBODIMENTS

Descriptions are provided hereinbelow for embodiments based on thedrawings. In the respective drawings referenced herein, the sameconstituents are designated by the same reference numerals and duplicateexplanation concerning the same constituents is omitted. All of thedrawings are provided to illustrate the respective examples only.

FIG. 1 is a plan view showing semiconductor light emission device 100 ofa first embodiment of the invention. FIG. 2 is an enlarged plan viewshowing semiconductor light emission device 100 shown in FIG. 1. FIG. 3is a cross-sectional view taken along the line III-III in a directionindicated by arrows shown in FIG. 2. FIG. 4 is a cross-sectional viewtaken along the line IV-IV in a direction indicated by arrows shown inFIG. 2. FIG. 5 is a plan view showing thin-film semiconductor lightemission element 101 of semiconductor light emission device 100 shown inFIG. 2.

Semiconductor light emission device 100 shown in FIG. 1 forms imagedisplay apparatus 10 such as an HUD (head-up display), a portableterminal or a projector, for example. Semiconductor light emissiondevice 100 has thin-film semiconductor light emission elements 101disposed in a matrix on later-described mount substrate 109 (FIG. 3).Here, a row direction is an X direction, and a column direction is a Ydirection.

Thin-film semiconductor light emission elements 101 in each column areconnected to anode common wiring 106 in common. Each anode common wiring106 is connected to anode extraction pad 107. Thin-film semiconductorlight emission elements 101 in each row are connected to cathode commonwiring 103 in common. Each cathode common wiring 103 is connected tocathode extraction pad 102. Light emission of each of thin-filmsemiconductor light emission elements 101 is controlled through anodecommon wiring 106 and cathode common wiring 103, and thus atwo-dimensional image can be displayed.

As shown in FIG. 2, thin-film semiconductor light emission element 101includes anode thin-film wiring 105 connected to anode common wiring106, and cathode thin-film wiring 108 connected to cathode common wiring103. Each of anode thin-film wiring 105 and cathode thin-film wiring 108is formed in a rectangular shape (oblong shape). Note that a connectionportion (opening portion 104 a) between cathode thin-film wiring 108 andcathode common wiring 103 is shown in FIG. 4 described later.

Anode common wiring 106 and cathode common wiring 103 are formed ofTi/Pt/Au or Ti/Pt/AuGeNi, for example. Note that as for notation ofwiring materials, a layer on the left side of the slash is located belowa layer on the right side of the slash. In the same manner as anodecommon wiring 106 and cathode common wiring 103, anode thin-film wiring105 and cathode thin-film wiring 108 are also formed of Ti/Pt/Au orTi/Pt/AuGeNi, for example.

As shown in FIG. 3, thin-film semiconductor light emission element 101includes light emission layer 113, upper and lower two layers of players 112 a, 112 b formed with light emission layer 113 interposedtherebetween in an upper and lower direction, anode electrode 118 formedon an upper side of p layer 112 a, and n contact layer 114 formed on alower side of p layer 112 b.

Light emission layer 113 is a multiple quantum well (MQW) layer havingan InGaN layer and a GaN layer, or is a multiple quantum well layerhaving an AlGaInP layer, for example. P layers 112 a, 112 b are formedof p-GaN or p-GaP, for example. N contact layer 114 is formed of n-GaNor n-GaAs, for example. Anode electrode 118 is formed of ITO (indium tinoxide), IZO (indium zinc oxide) or Ni/Au, for example.

A stacked body including light emission layer 113 and p layers 112 a,112 b described above is subjected to patterning by later-describedetching so as to expose n contact layer 114. In addition, interlayerdielectric film 116 is provided to cover exposed n contact layer 114 andthe stacked body (light emission layer 113 and p layers 112 a, 112 b).Interlayer dielectric film 116 is an inorganic dielectric film such asSiN, SiO₂ and Al₂O₃, or is an organic dielectric film such as apolyimide, an epoxy or an acrylic.

Interlayer dielectric film 116 includes openings (contact holes) at apredetermined spot on anode electrode 118, and at a predetermined spot(FIG. 4) on n contact layer 114.

As shown in FIG. 4, cathode connection pads 115 are formed on n contactlayer 114 so as to be located at the opening of interlayer dielectricfilm 116. Each cathode connection pad 115 is formed of Ti/Al orTi/Pt/AuGeNi, for example.

Additionally, anode connection pad 111 is formed on interlayerdielectric film 116 formed on n contact layer 114. Anode connection pad111 is formed of Ti/Al or Ti/Pt/AuGeNi, for example. Anode connectionpad 111 and cathode connection pad 115 are formed to have substantiallythe same height (in other words, are substantially flush with eachother).

In addition, connection portion 119 (FIG. 3) is formed from anodeconnection pad 111 to an upper surface of anode electrode 118.Connection portion 119 is connected to anode electrode 118 through theopening of interlayer dielectric film 116 on anode electrode 118.

As shown in FIG. 5, each of anode connection pad 111 and cathodeconnection pad 115 has a large area, such as 5 μm×13 μm, for example.This is for the purpose of facilitating electric connection even whenmisalignment occurs in mounting thin-film semiconductor light emissionelement 101 onto mount substrate 109. For this reason, when anodeconnection pad 111 and cathode connection pad 115 are formed in a simpleoblong shape (stereotypical shape), a stress may be applied to thin-filmsemiconductor light emission element 101 due to the later-describedthermal contraction.

Accordingly, in the embodiment, anode connection pad 111 and cathodeconnection pad 115 each have a microstructure portion or a fine shapedportion (finely processed portion). To be more specific, anodeconnection pad 111 and cathode connection pad 115 each have a meshshape, i.e. a shape having opening portions (mesh holes) arrangedtwo-dimensionally. With this formation, a stress applied to thin-filmsemiconductor light emission element 101 is reduced.

Referring back to FIG. 3, mount substrate 109 on which thin-filmsemiconductor light emission element 101 is to be mounted includes asemiconductor substrate such as Si, GaAs, GaP, InP, GaN and ZnO, aceramic substrate such as AlN and Al₂O₃, a glass epoxy substrate, ametal substrate such as Cu and Al, or a plastic substrate, for example.

Dielectric film 110 made of Si or SiO₂, for example, is formed on mountsubstrate 109. Cathode common wiring 103 described above is formed ondielectric film 110. Flattened film 104 which is made of a polyimide orepoxy resin, for example, and which has a surface roughness of 5 nm orless is formed to cover cathode common wiring 103. Thin-filmsemiconductor light emission element 101 is fixed to a surface offlattened film 104 by an intermolecular force.

Interlayer dielectric film 117 is formed to cover thin-filmsemiconductor light emission element 101 mounted on mount substrate 109.Interlayer dielectric film 117 is a photosensitive organic dielectricfilm or an inorganic dielectric film. Note that interlayer dielectricfilm 117 is omitted in the plan views in FIG. 1 and FIG. 2.

Next, a manufacturing method of semiconductor light emission device 100is described. First, a sacrifice layer made of AlGaAs, for example, isformed on a growth substrate other than mount substrate 109, and ncontact layer 114, p layer 112 b, light emission layer 113, p layer 112a and anode electrode 118 are stacked in that order on the sacrificelayer. Then, the stacked body is etched to expose n contact layer 114.Thereafter, interlayer dielectric film 116 is formed to cover thestacked body and exposed n contact layer 114.

Subsequently, interlayer dielectric film 116 is partially removed byphotolithography or etching to form openings for connection to anodeelectrode 118 and n contact layer 114. Moreover, film formation of eachof anode connection pad 111 and cathode connection pad 115 is carriedout at a predetermined spot on n contact layer 114 by metal vapordeposition or sputtering, and then patterning is performed thereon bylift-off or etching. Anode connection pad 111 and cathode connection pad115 each have a mesh shape as described above.

Note that, as shown in FIG. 4, cathode connection pad 115 is connectedto n contact layer 114 through the opening of interlayer dielectric film116. On the other hand, anode connection pad 111 is formed on interlayerdielectric film 116 and is not in contact with n contact layer 114. Inaddition, connection portion 119 (FIG. 3) is formed together with anodeconnection pad 111, and is connected to anode electrode 118 through theopening of interlayer dielectric film 116.

After an LED (light-emitting diode) structure is formed as describedabove, the sacrifice layer is removed by etching. Thus, the LEDstructure is separated from the growth substrate. Note that thesacrifice layer (AlGaAs, for example) is a layer to be selectivelyremoved from the LED structure and the growth substrate by usinghydrofluoric acid, for example, as an etchant. The LED structure thusseparated from the growth substrate is thin-film semiconductor lightemission element 101.

On the other hand, dielectric film 110 is formed on mount substrate 109,then cathode common wiring 103 is formed on dielectric film 110, andflattened film 104 is formed on cathode common wiring 103 in such a wayas to have a surface roughness of 5 nm or less.

Then, the LED structure (thin-film semiconductor light emission element101) separated from the growth substrate is fixed to flattened film 104on mount substrate 109 by an intermolecular force. Thereby, thin-filmsemiconductor light emission element 101 is mounted on mount substrate109.

After thin-film semiconductor light emission element 101 is mounted onmount substrate 109, interlayer dielectric film 117 is formed to coverthem. When interlayer dielectric film 117 is a photosensitive organicdielectric film, photolithography is performed. When interlayerdielectric film 117 is an inorganic dielectric film, etching isperformed after film formation. Thereby, an opening is formed above eachof anode connection pad 111 and cathode connection pad 115.

Thereafter, anode thin-film wiring 105 and cathode thin-film wiring 108are formed on interlayer dielectric film 117. At this time, anodethin-film wiring 105 is connected to anode connection pad 111 andcathode thin-film wiring 108 is connected to cathode connection pad 115,through the openings formed in interlayer dielectric film 117.

Cathode thin-film wiring 108 is connected to cathode common wiring 103at opening 104 a (FIG. 4) formed in interlayer dielectric film 117 andflattened film 104. In addition, anode common wiring 106 is connected toanode thin-film wiring 105. Anode common wiring 106 and cathode commonwiring 103 are respectively connected to anode extraction pad 107 andcathode extraction pad 102, as shown in FIG. 1.

Next, effects of the first embodiment are described in comparison with acomparative example. First, a semiconductor light emission device of thecomparative example is described.

FIG. 6 is a plan view showing the semiconductor light emission device ofthe comparative example. Semiconductor light emission device 800 shownin FIG. 6 is formed by mounting thin-film semiconductor light emissionelement 801 on mount substrate 809. Light emission portion 803 and anodeconnection pad 806 are formed in thin-film semiconductor light emissionelement 801. Note that drawings and descriptions of a cathode connectionpad are omitted. Wiring portion 804 including a drive circuit is formedin mount substrate 809.

Thin-film semiconductor light emission element 801 and mount substrate809 are covered with an unillustrated interlayer dielectric film.Openings 805, 808 corresponding respectively to wiring portion 804 andanode connection pad 806 are formed in the interlayer dielectric film.In addition, thin-film wiring 807 electrically connecting anodeconnection pad 806 and wiring portion 804 to each other is formed on theinterlayer dielectric film.

Anode connection pad 806 is made of a metal, and has a simple oblongshape which is larger in area than light emission portion 803. For thisreason, when a temperature change occurs in the manufacturing process ofthin-film semiconductor light emission element 801, anode connection pad806 thermally contracts more than other parts of thin-film semiconductorlight emission element 801. Accordingly, a stress acts on thin-filmsemiconductor light emission element 801 in an in-plane direction, andthereby cracks or warpage may occur in thin-film semiconductor lightemission element 801. In addition, when warpage of thin-filmsemiconductor light emission element 801 is large, thin-filmsemiconductor light emission element 801 may peel off from mountsubstrate 809 in mounting thin-film semiconductor light emission element801 onto mount substrate 809.

On the other hand, in the first embodiment (FIGS. 1 to 5) as describedabove, since anode connection pad 111 and cathode connection pad 115each have a mesh shape, thermal contraction can be suppressed ascompared with the case where each connection pad has a simple oblongshape. For this reason, the occurrence of cracks or warpage in thin-filmsemiconductor light emission element 101 can be suppressed. Accordingly,thin-film semiconductor light emission element 101 can be prevented frompeeling off from mount substrate 109.

As described above, in the first embodiment of the invention, sinceanode connection pad 111 and cathode connection pad 115 of thin-filmsemiconductor light emission element 101 each have a fine shaped portionor a maze shaped portion (mesh shape in the first embodiment), a stressapplied to thin-film semiconductor light emission element 101 along withthermal contraction of each connection pad 111, 115 is reduced. As aresult, the occurrence of cracks or warpage in thin-film semiconductorlight emission element 101 is prevented, and thus thin-filmsemiconductor light emission element 101 can be prevented from peelingoff from mount substrate 109.

Additionally, each connection pad 111, 115 has a large area as a whole.For this reason, even when misalignment occurs in mounting thin-filmsemiconductor light emission element 101 onto mount substrate 109,connection pads 111, 115 can be electrically connected respectively tocommon wirings 106, 103 easily.

In addition, each connection pad 111, 115 has a mesh shape, and has acontinuous metal layer (parts other than the mesh holes). For thisreason, conduction is secured all over the connection pad, and thefunctions of the connection pads can be fully carried out.

Note here that although a description is given of the case where bothanode connection pad 111 and cathode connection pad 115 each have a fineshaped portion (mesh shape in the first embodiment), only one of themmay have a fine shaped portion.

Second Embodiment

FIG. 7 is a plan view showing thin-film semiconductor light emissionelement 101 of a second embodiment of the invention. The same componentsas those of the first embodiment are denoted by the same referencenumerals. In the second embodiment, configurations of anode connectionpad 211 and cathode connection pad 215 are different from those in thefirst embodiment.

Anode connection pad 111 and cathode connection pad 115 of the firstembodiment as described above each have a mesh shape. In contrast, anodeconnection pad 211 and cathode connection pad 215 of the secondembodiment each have a striped pattern shape.

In other words, in each of anode connection pad 111 and cathodeconnection pad 115 of the first embodiment, openings through which afront surface and a back surface of the pad communicate with each otherare each formed in a substantially square shape and disposed in amatrix, whereas, in anode connection pad 211 and cathode connection pad215 of the second embodiment, openings through which a front surface anda back surface of the pad communicate with each other are each formed ina rectangular shape long in a Y direction and arranged in a direction (Xdirection) perpendicular to the Y direction.

To be specific, anode connection pad 211 has a shape in which slits longin the Y direction and opened to an external edge (side surface) ofanode connection pad 211 are arranged in the X direction. In otherwords, anode connection pad 211 has a shape in which elongated portionslong in the Y direction are arranged in parallel, and one end (here, anend portion on the anode electrode 118 side) in the Y direction of eachelongated portion is connected to another. Cathode connection pad 215also has a similar shape to that of anode connection pad 211.

Each of anode connection pad 211 and cathode connection pad 215 isformed in the following manner. Film formation is carried out by metalvapor deposition or sputtering, and then patterning is performed thereonby lift-off or etching, as in the first embodiment.

In the second embodiment, anode connection pad 211 and cathodeconnection pad 215 each have a striped pattern shape. For this reason,as compared with a stereotypical shape as in the comparative example(FIG. 6), thermal contraction occurring along with a temperature changecan be suppressed and thus a stress applied to thin-film semiconductorlight emission element 101 can be reduced. Accordingly, cracks orwarpage of thin-film semiconductor light emission element 101 can besuppressed, and thus thin-film semiconductor light emission element 101can be prevented from peeling off from mount substrate 109.

Additionally, in the second embodiment, each connection pad 211, 215 hasa shape in which slits extend to an external edge of each connection pad211, 215. In other words, regions (portions of slits) where no metallayer exists are not closed by the metal layer. For this reason, theresist is not isolated in patterning each connection pad 211, 215, andhence formation of each connection pad 211, 215 by lift-off is easy.

As described above, in the second embodiment of the invention, anodeconnection pad 211 and cathode connection pad 215 of thin-filmsemiconductor light emission element 101 each have a striped patternshape. For this reason, a stress applied to thin-film semiconductorlight emission element 101 along with thermal contraction of eachconnection pad 211, 215 is reduced. As a result, it is possible toprevent the occurrence of cracks in thin-film semiconductor lightemission element 101, and to prevent thin-film semiconductor lightemission element 101 from peeling off from mount substrate 109.

In addition, each connection pad 211, 215 has a large area as a whole.For this reason, even when misalignment occurs in mounting thin-filmsemiconductor light emission element 101 onto mount substrate 109,connection pads 211, 215 can be electrically connected respectively tocommon wirings 106, 103 easily.

Moreover, in each connection pad 211, 215, regions where no metal layerexists are not closed by the metal layer. For this reason, formation ofeach connection pad 211, 215 by lift-off is easy. Accordingly, eachconnection pad 211, 215 can be formed by using Au, Pt or the like (bylift-off) on which patterning is difficult to perform by etching.

Modified Examples

In the second embodiment, although the connection pad with a verticallystriped pattern shown in FIG. 7 is described, modifications shown inFIG. 8 and FIGS. 9A, 9B, and 9C may be made.

In the modified example shown in FIG. 8, each of anode connection pad411 and cathode connection pad 415 has a striped pattern shape in whichelongated portions long in the X direction are arranged in the Ydirection. In other words, each of anode connection pad 411 and cathodeconnection pad 415 has a shape in which slits long in the X directionand opened to an external edge (side surface) thereof are arranged inthe Y direction.

Moreover, in the modified example shown in FIG. 9A, each of anodeconnection pad 511 and cathode connection pad 515 is formed in arectangular spiral shape. In other words, in each of anode connectionpad 511 and cathode connection pad 515, a slit opened to an externaledge (side surface) extends to form a rectangular spiral shape.

Furthermore, in the modified examples shown in FIG. 9B and FIG. 9C, eachof anode connection pad 611 and cathode connection pad 615 is formed ina diffraction pattern.

In these modified examples as well, a stress applied to thin-filmsemiconductor light emission element 101 along with thermal contractionof each connection pad 411, 415, 511, 515, 611, 615 is reduced.Accordingly, it is possible to prevent the occurrence of cracks orwarpage in thin-film semiconductor light emission element 101, and toprevent thin-film semiconductor light emission element 101 from peelingoff from mount substrate 109.

Additionally, in each connection pad 411, 415, 511, 515 shown in FIG. 8and FIG. 9A, since each slit is opened to an external edge (sidesurface) thereof, formation of each connection pad 411, 415, 511, 515 bylift-off is easy, as in the second embodiment described above.

Third Embodiment

FIG. 10 and FIG. 11 are cross-sectional views showing semiconductorlight emission device 100 of a third embodiment of the invention. FIG.10 corresponds to a cross-sectional view taken along the line III-III ina direction indicated by arrows shown in FIG. 2. FIG. 11 corresponds toa cross-sectional view taken along the line IV-IV in a directionindicated by arrows shown in FIG. 2. The same components as those of thefirst or second embodiment are denoted by the same reference numerals.

In the embodiment, interlayer dielectric film 316 formed on n contactlayer 114 and interlayer dielectric film 317 formed on thin-filmsemiconductor light emission element 100 are formed of materials havingetch selectivity therebetween. Each interlayer dielectric film 316, 317is made of an inorganic dielectric film such as SiN, SiO₂ or Al₂O₃, oris an organic dielectric film such as a polyimide, an epoxy or anacrylic. Preferred examples of combinations of interlayer dielectricfilms 316, 317 having etch selectivity therebetween include acombination of Al₂O₃ and SiN, a combination of Al₂O₃ and SiO₂, acombination of SiN and polyimide, and the like.

Al₂O₃ can be patterned by hot phosphoric acid or the like, and has aresistance to CF₄ dry etching. Moreover, SiN and SiO₂ can be patternedby CF₄ dry etching, and have a resistance to hot phosphoric acid.Furthermore, polyimide can be patterned by photolithography, and has aresistance to hot phosphoric acid and CF₄ dry etching.

As described above, interlayer dielectric films 316, 317 are formed by acombination of two types of interlayer dielectric films having etchselectivity therebetween. For this reason, when interlayer dielectricfilm 317 is formed and patterned after thin-film semiconductor lightemission element 101 is mounted on mount substrate 109, interlayerdielectric film 316 which has already been formed is not etched.Accordingly, in the formation of anode thin-film wiring 105, n contactlayer 119 below anode connection pad 111 is not exposed and thus a shortcircuit can be prevented.

Note that in the third embodiment, shapes of anode connection pad 111and cathode connection pad 115 may be any shapes described in the firstand second embodiments or modified examples thereof.

As described above, in the third embodiment of the invention, interlayerdielectric films 316, 317 are formed by a combination of interlayerdielectric films having etch selectivity therebetween. Accordingly, whenone interlayer dielectric film is etched, the other interlayerdielectric film is prevented from being etched, in addition to theeffects described in the first and second embodiments. For this reason,a short circuit between anode thin-film wiring 105 and n contact layer114 can be prevented, for example.

Semiconductor light emission device 100 using thin-film semiconductorlight emission element 101 of the embodiments as described above can beemployed in an HUD (head-up display), a portable terminal, a projectoror the like as a two-dimensional array light source, for example. Thus,it is possible to reduce power consumption, and to achieve an imagedisplay with high luminance and high definition.

Additionally, semiconductor light emission device 100 using thin-filmsemiconductor light emission element 101 of the embodiments as describedabove can be employed in an image display apparatus such as an HMD (headmount display) or in an image formation apparatus such as anelectrophotographic printer, as a one-dimensional array light source,for example.

Next, a description is given of a configuration example of an imageformation apparatus employing semiconductor light emission device 100using thin-film semiconductor light emission element 101 of theembodiments.

FIG. 12 is a cross-sectional view showing an example in whichsemiconductor light emission device 100 of the above-described first,second or third embodiment is employed in print head 20 of an imageformation apparatus.

Print head (LED array head) 20 shown in FIG. 12 is a print head in whichsemiconductor light emission device 100 of the first, second or thirdembodiment is mounted on base member 21. Thin-film semiconductor lightemission elements 101 of semiconductor light emission device 100 arearranged one-dimensionally (may be arranged in the row direction X or inthe column direction Y shown in FIG. 1).

Rod lens array 22 serving as an optical element configured to collectlight emitted from thin-film semiconductor light emission element 101 isplaced above semiconductor light emission device 100. Rod lens array 22is a rod lens array in which optical lens elements are arranged in anarrangement direction of thin-film semiconductor light emission elements101, and is held at a predetermined position by lens holder 23 servingas an optical element holder.

Lens holder 23 is formed to cover base member 21 and semiconductor lightemission device 100. Base member 21, semiconductor light emission device100 and lens holder 23 are integrally held by clamper 24.

Light emitted from semiconductor light emission device 100 is applied toa surface of later-described photosensitive drum 41 through rod lensarray 22, and is used to form an electrostatic latent image.

FIG. 13 is a diagram showing a configuration example of image formationapparatus 30 using print head 20 shown in FIG. 12.

Image formation apparatus 30 is a color electrophotographic printer, forexample, and includes process units 40Y, 40M, 40C, 40K configured toform images of yellow, magenta, cyan and black. Process units 40Y, 40M,40C, 40K are disposed along conveyance path 39 of media P such as printsheets. Since process units 40Y, 40M, 40C, 40K have a commonconfiguration, a configuration of process unit 40C of cyan is taken asan example and described.

Process unit 40C includes photosensitive drum 41 serving as an imagecarrier rotatable in a clockwise direction in the drawing. Charge device42, print head (exposure device) 20, development device 43, and cleaningdevice 44 are disposed around photosensitive drum 41 in a rotationdirection thereof. Charge device 42 is configured to uniformly charge asurface of photosensitive drum 41. Print head (exposure device) 20 isconfigured to form an electrostatic latent image by selectively applyinglight to the surface of photosensitive drum 41. Development device 43 isconfigured to develop the electrostatic latent image formed on thesurface of photosensitive drum 41, by using a toner of a predeterminedcolor (cyan). Cleaning device 44 is configured to remove the tonerremaining on the surface of photosensitive drum 41.

Media cassette 31 configured to house media P is installed in a lowerpart of image formation apparatus 30. Feed roller 32 is disposed abovemedia cassette 31 and is configured to separately feed media P, one byone, housed in media cassette 31. Moreover, paired conveyance rollers33, 34 configured to convey each medium P to process units 40Y, 40M,40C, 90K are disposed in a conveyance direction of medium P fed by feedroller 32.

Transfer roller 45 is disposed at a position opposed to eachphotosensitive drum 41 of process units 40Y, 40M, 40C, 40K. In order totransfer a toner image on photosensitive drum 41 to medium P, apredetermined potential difference is provided between a surface ofphotosensitive drum 41 and a surface of transfer roller 45.

Fixation device 35 is disposed on a downstream side of process units40Y, 40M, 40C, 40K along conveyance path 39. Fixation device 35 includesa heat roller and a back-up roller, and is configured to fix the tonertransferred onto medium P by pressure and heating. In addition, paireddelivery rollers 36, 37 configured to convey medium P delivered fromfixation device 35 to stacker portion 38 provided outside imageformation apparatus 30 are disposed on a downstream side of fixationdevice 35.

Next, operations of image formation apparatus 30 are described. First,media P housed in media cassette 31 are separately fed, one by one, toconveyance path 39 by feed roller 32. Each medium P fed to conveyancepath 39 is conveyed to a nip portion between transfer roller 45 andphotosensitive drum 41 of process unit 40Y by paired conveyance rollers33, 34.

In process unit 40Y, a surface of photosensitive drum 41 is uniformlycharged by charge device 42. Moreover, each thin-film semiconductorlight emission element 101 (FIG. 12) of print head 20 emits light inaccordance with image information. Thereby, the surface ofphotosensitive drum 41 is exposed to light, and thus an electrostaticlatent image is formed. The electrostatic latent image formed onphotosensitive drum 41 is developed by development device 43 to be atoner image. When medium P passes through a nip between photosensitivedrum 41 and transfer roller 45, the toner image on the surface ofphotosensitive drum 41 is transferred to medium P.

Medium P passes through process units 40M, 40C, 40K in the same manneras described above, and the toner image on each photosensitive drum 41is sequentially transferred to the surface of medium P.

Medium P to which the toner images are transferred is conveyed tofixation device 35, and the toner images are fixed to medium P by heatand pressure. Medium P to which the toner images are fixed is deliveredto stacker portion 38 by paired delivery rollers 36, 37. Thereby, acolor image is formed on medium P.

Note that it is needless to say that a semiconductor light emissiondevice of the above-described embodiments can be employed in an imageformation apparatus other than the above-described colorelectrophotographic printer.

The invention includes other embodiments in addition to theabove-described embodiments without departing from the spirit of theinvention. The embodiments are to be considered in all respects asillustrative, and not restrictive. The scope of the invention isindicated by the appended claims rather than by the foregoingdescription. Hence, all configurations including the meaning and rangewithin equivalent arrangements of the claims are intended to be embracedin the invention.

What is claimed is:
 1. A semiconductor light emission device,comprising: a substrate; and semiconductor light emission elementsmounted on the substrate, each semiconductor light emission elementincluding an anode connection pad and a cathode connection pad, whereinone of the anode connection pad and the cathode connection pad has afine shaped portion.
 2. The semiconductor light emission deviceaccording to claim 1, further comprising an anode common wiring and acathode common wiring provided above the substrate, wherein the anodeconnection pads of the semiconductor light emission elements areelectrically connected with the anode common wiring by a first thin-filmwiring, and the cathode connection pads of the semiconductor lightemission elements are electrically connected with the cathode commonwiring by a second thin-film wiring.
 3. The semiconductor light emissiondevice according to claim 1, wherein the anode connection pad and thecathode connection pad are formed above a single layer, with a firstinterlayer dielectric film interposed between the anode connection padand the single layer, and without the first interlayer dielectric filminterposed between the cathode connection pad and the single layer. 4.The semiconductor light emission device according to claim 1, whereinthe fine shaped portion is formed to have one from the group of a meshshape, a striped pattern, a diffraction pattern and a spiral shape. 5.The semiconductor light emission device according to claim 1, whereinone of the anode connection pad and the cathode connection pad is formedof a film deposited by metal vapor deposition or sputtering, andpatterned by etching or lift-off.
 6. The semiconductor light emissiondevice according to claim 1, wherein the semiconductor light emissionelement is a thin film.
 7. The semiconductor light emission deviceaccording to claim 1, wherein the semiconductor light emission elementis fixed to the substrate by an intermolecular force.
 8. Thesemiconductor light emission device according to claim 2, wherein thefirst thin-film wiring and the second thin-film wiring are each in arectangular shape.
 9. The semiconductor light emission device accordingto claim 3, wherein the first interlayer dielectric film is made of oneof an inorganic dielectric film and an organic dielectric film.
 10. Thesemiconductor light emission device according to claim 3, furthercomprising a second interlayer dielectric film formed on thesemiconductor light emission element, wherein the first interlayerdielectric film and the second interlayer dielectric film are formed ofa combination of interlayer dielectric films having etch selectivitytherebetween.
 11. The semiconductor light emission device according toclaim 1, wherein the fine shaped portion is processed to be finer than aconnection portion connecting the fine shaped portion and thesemiconductor light emission element with each other.
 12. Thesemiconductor light emission device according to claim 1, wherein thefine shaped portion formed in one of the anode connection pad and thecathode connection pad comprises openings through which a front surfaceand a back surface of the one pad communicate with each other.
 13. Thesemiconductor light emission device according to claim 12, wherein eachof the openings is in a slit shape opened to a side surface of the onepad.
 14. The semiconductor light emission device according to claim 12,wherein each of the openings of the fine shaped portion is smaller thanan opening for a connection portion connecting the fine shaped portionand the semiconductor light emission element with each other.
 15. Animage display apparatus, comprising the semiconductor light emissiondevice according to claim
 1. 16. An image formation apparatus,comprising the semiconductor light emission device according to claim 1.17. An image formation apparatus, comprising: an exposure deviceincluding the semiconductor light emission device according to claim 1,an image carrier on a surface of which a latent image is formed by theexposure device, and a development device configured to attach adeveloper to the latent image on the surface of the image carrier, andthereby form a developer image on the surface of the image carrier. 18.A semiconductor light emission device, comprising: a substrate; andsemiconductor light emission elements mounted on the substrate, eachincluding an anode connection pad and a cathode connection pad, whereinone of the anode connection pad and the cathode connection pad has oneor more openings through which a front surface and a back surface of theone pad communicate with each other.
 19. The semiconductor lightemission device according to claim 18, wherein each of the openingsformed in the one pad is in a slit shape opened to a side surface of theone pad.